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Katsuya Inoue

Publications and source records attributed to Katsuya Inoue.

14 recordsLinked to original sources
PubMed2006

Hybrid organic-inorganic conductor with a magnetic chain anion: kappa-BETS2[Fe(III)(C2O4)Cl2] [BETS = bis(ethylenedithio)tetraselenafulvalene].

The synthesis, crystal structure, and electrical, optical, and magnetic properties of kappa-BETS2[Fe(III)(C2O4)Cl2], where BETS is bis(ethylenedithio)tetraselenafulvalene, are reported. The black plate crystals consist of parallel donor layers, two per unit cell, displaying a kappa-type packing of BETS(0.5+) within the bc plane and anionic magnetic chains, [Fe(C2O4)Cl2-]n, running along the c axis. It displays metallic behavior down to 4.2 K, and analysis of the optical reflectivity data gives unscreened plasma energies of 0.69 eV (E parallel c) and 0.40 eV (E perpendicular c). The optical anisotropy is larger than that seen for other kappa phases and is described well by transfer integrals obtained from extended Hückel calculations. However, the transfer integrals need to be scaled down uniformly by a factor of 1.21 to reproduce the absolute experimental plasma frequencies. The band structure consists of a one-dimensional (1D) band and a hole pocket, characteristics of kappa phases. The magnetic properties were modeled by the sum of a 1D antiferromagnetic chain contribution from the d spins of Fe3+, a temperature-independent paramagnetic contribution, and a Curie impurity term. At 4.5 K, there is a signature of long-range magnetic ordering to a canted-antiferromagnetic state in the zero-field-cooled-field-cooled magnetizations, and at 2 K, a small hysteresis loop is observed.

Journal Article↗
PubMed2006

Metal-organic frameworks from homometallic chains of nickel(II) and 1,4-cyclohexanedicarboxylate connectors: ferrimagnet-ferromagnet transformation.

The hydrothermal reactions of nickel(II) nitrate with a mixture of the geometric cis and trans isomers of 1,4-cyclohexanedicarboxylic acid (1,4-chdc or C6H10(COOH)2) and a base yield three structurally different complexes, [Ni3(mu3-OH)2(mu4-cis-1,4-chdc)2(H2O)4].2H2O (1), [Ni(3)(mu3-OH)2(mu4-trans-1,4-chdc)2(H2O)4].4H2O (2), and [Ni(H2O)4(mu2-trans-1,4-chdc)], depending on the reaction conditions. The single-crystal X-ray structure analyses of 1 and 2 reveal segregation of the isomers and formation of frameworks based on infinite Ni3(OH)2(H2O)4 chains, acting as secondary building units, connected by either cis- or trans-chdc for 1 and 2, respectively. The frameworks sustain channels that house two or four water molecules, respectively, according to the size and shape of the channels that depend on the particular isomer. The structure of 3 consists of chains of square-planar Ni(H2O)4 bridged by trans-chdc. Magnetic data as a function of temperature and field of the virgin samples for 1 indicate long-range ordering (LRO) to a ferrimagnetic ground state at 2.1 K that is reversibly transformed into a ferromagnet below 4.4 K upon partial dehydration and rehydration. Powder X-ray diffraction of 1, in its virgin state, after dehydration and after rehydration, confirms the stability of the framework. The magnetic data for 2 tend toward a LRO state to possibly a ferrimagnet below 2 K. The temperature dependence of the susceptibility of the two compounds is accounted for by the presence of both ferro- and antiferromagnetic exchanges within each chain via Ni-O-Ni and Ni-O-C-O-Ni pathways and weak coupling between neighboring chains via the 1,4-chdc unit. 3 is a uniform s = 1 antiferromagnetic chain (J/kB = 2.27(1) K).

Journal Article↗
PubMed2005

Spin-crossover cobalt(II) compound with banana-shaped structure.

A banana-shaped spin-crossover (SCO) cobalt(II) complex [Co(C16-terpy)2](BPh4)2 (1) with long alkyl chains, based on a terpyridine frame, was synthesized. Compound 1 exhibited very gradual SCO behavior and changes in the dielectric constant. This shows a way in which SCO materials can be used in electronic devices.

Journal Article↗
PubMed2005

Molecular rotor of Cs2([18]crown-6)3 in the solid state coupled with the magnetism of [Ni(dmit)2].

Nanoscale molecular rotors that can be driven in the solid state have been realized in Cs2([18]crown-6)3[Ni(dmit)2]2 crystals. To provide interactions between the molecular motion of the rotor and the electronic system, [Ni(dmit)2]- ions, which bear one S=1/2 spin on each molecule, were introduced into the crystal. Rotation of the [18]crown-6 molecules within a Cs2([18]crown-6)3 supramolecule above 220 K was confirmed using X-ray diffraction, NMR, and specific heat measurements. Strong correlations were observed between the magnetic behavior of the [Ni(dmit)2]- ions and molecular rotation. Furthermore, braking of the molecular rotation within the crystal was achieved by the application of hydrostatic pressure.

Journal Article↗
PubMed2005

Knotted network consisting of 3-threads and a zwitterionic one-dimensional polymorphs of trans-3-(3-pyridyl)acrylate of cobalt and nickel, MII(C8H6NO2)2(H2O)2.

We present the hydrothermal synthesis, characterization (IR, DT-TGA), single-crystal structures, and magnetic properties of two polymorphs of trans-3(3-pyridyl)acrylate of cobalt(II) and of nickel(II), M(II)(C(8)H(6)NO(2))(2)(H(2)O)(2). Hydrothermal reaction at 120 or 170 degrees C results exclusively in the different polymorphs. The infrared spectra and thermogravimetric analyses of the complexes are almost similar for the two polymorphs but show a difference between cobalt and nickel in energies of the vibrational modes and in the decomposition temperatures. The crystal structures of the two polymorphs are quite different; one crystallizes in a monoclinic space group and the other in a triclinic. This major difference is due to the different stereochemistry, cis or trans, of the coordination at the metal sites. When it is trans-MN(2)O(4), it results in the monoclinic cell consisting of a 3D-network of metals bridged by the ligands through single bonds (M-N and M-O). There is threading of three sublattices up to 2a x 4b x 2c, at which point the three sublattices are knotted into one infinite framework. When it is cis-MN(2)O(4), it results in the triclinic cell and consists of Zwitterionic linear chains of metals bridged by one single ligand via the pyridine and a bidentate carboxylate group and the other ligand is bonded only via the pyridine while its carboxylate end is free. All four compounds are paramagnetic with Weiss constants suggesting weak interactions.

Journal Article↗
PubMed2004

1-D cobalt(II) spin transition compound with strong interchain interaction: [Co(pyterpy)Cl(2)].X.

Cobalt(II) compounds [Co(pyterpy)Cl(2)].MeOH (1.(MeOH)) and [Co(pyterpy)Cl(2)].2H(2)O (1.(2H(2)O)) were synthesized. The compound 1.(MeOH) forms the quasi 3-D networks by making pi-pi stacking between the 1-D chains. The methanol molecules from 1.(MeOH) can be removed by heating, and substituted by absorption of water molecules. The MeOH molecules in 1.(MeOH) are removed by heating at 410 K, and they are substituted by water molecules to form 1.(2H(2)O). 1.(2H(2)O) exhibits a S = (3)/(2) (HS) left arrow over right arrow S = (1)/(2) (LS) spin transition with a thermal hysteresis. We have succeeded in constructing a guest dependent 1-D spin-crossover cobalt(II) compound.

Journal Article↗
PubMed2004

Anionic NaCl-type frameworks of [Mn(II)(HCOO)(3)(-)], templated by alkylammonium, exhibit weak ferromagnetism.

We present the synthesis, characterization by IR, TGA, single crystal X-ray structure and magnetic properties of a novel series of NaCl-type frameworks of [AmineH(+)][Mn(HCOO)(3)(-)], templated by alkylammonium. The anionic NaCl-framework of [Mn(HCOO)(3)(-)] is counter-balanced by the alkylammonium cations located in the cavities of the framework to which they are hydrogen-bonded. The divalent manganese ions have octahedral geometry and are bridged by the formate in an anti-anti mode of coordination. All the compounds exhibit long-range antiferromagnetism below 9 K with a slight non-collinear arrangement of the moments. The canting, likely due to second-order spin-orbit coupling, is via a Dzyaloshinski-Moriya antisymmetric exchange mechanism. A spin-flop is observed in each case at fairly low fields. An orthorhombic to monoclinic transformation was observed for the protonated cyclotrimethyleneamine that is accompanied by localization of the cations into two positions below 240 K from the rapid dynamic flipping of the ring observed at room temperature.

Journal Article↗
PubMed2004

Metal-complex assemblies constructed from the flexible hinge-like ligand H2bhnq: structural versatility and dynamic behavior in the solid state.

Novel metal-complex assemblies constructed from the flexible hinge-like ligand H(2)bhnq (H(2)bhnq=2,2'-bi(3-hydroxy-1,4-naphthoquinone)) have been synthesized. The X-ray crystal structures of these compounds reveal that four types of architectures are accessible by variation of the metal ions. In copper(II) compounds 1-3, the chelating bhnq(2-) ions bridge copper(II) centers to form one-dimensional zigzag chains. The chains of 1-3 are arranged by hydrogen-bonding interactions and stacking interactions to produce porous structures. Cobalt(II) and zinc(II) compounds 4 and 5 form one-dimensional helical chains. In 4 and 5, the crystal packing induces spontaneous resolution of the helical chains with chiral cavities formed perpendicular to the helices. Nickel(II) compounds 6 and 7 form cyclic tetramers. The fourth architecture, a dimer (compound 8), is obtained by the reaction of zinc(II) and bhnq(2-) in MeOH. In these compounds, changes of the dihedral angles and the metal-coordination mode of the bhnq(2-) ion induce the structural versatility. The assemblies of the zigzag chains of the copper(II) compounds exhibit reversible vapochromic behavior. UV/Vis, powder X-ray diffraction, EPR, and adsorption isotherm measurements indicate that this vapochromic behavior is based on the hinge-like flexibility of the bhnq(2-) ion.

Crystallography, X-Ray↗
PubMed2003

Design of novel inorganic-organic hybrid materials based on iron-chloranilate mononuclear complexes: characteristics of hydrogen-bond-supported layers toward the intercalation of guests.

Novel intercalation compounds constructed from the common two-dimensional hydrogen-bond-supported layers and functional guests [(H(0.5)phz)(2)[Fe(CA)(2)(H(2)O)(2)].2H(2)O](n)(1), ([Fe(Cp)(2)][Fe(CA)(2)(H(2)O)(2)])(n)(2), ([Fe(Cp*)(2)][Fe(CA)(2)(H(2)O)(2)])(n)(3), and [(TTF)(2)[Fe(CA)(2)(H(2)O)(2)]](n)(4) (H(2)CA = chloranilic acid, phz = phenazine, [Fe(Cp)(2)] = ferrocene, [Fe(Cp*)(2)] = decamethylferrocene, TTF = tetrathiafulvalene) are described. The guest cations are introduced between the ([Fe(CA)(2)(H(2)O)(2)](m-))(l) layers by electrostatic (1-4) and pi-pi stacking (3, 4) interactions. [Fe(Cp*)(2)](+) cations in 3 are stacked on each other making tilted columns which are included in the channel created by the chlorine atoms of CA(2-) dianions. TTF cations in 4 are stacked face to face with two types of S...S distances (type A; 3.579(3) A, and type B; 3.618(3) A) making a columnar structure. The TTF cations in the stacked column have a head-to-tail arrangement with respect to the iron-chloranilate layer. Mössbauer spectroscopy suggests that [Fe(CA)(2)(H(2)O)(2)](m-) anion in 3 is consistent with high-spin (S = 5/2) iron(III) ions and [Fe(Cp*)(2)](+) in the low-spin (S = 1/2) iron(III) ions. In 4, Mössbauer spectroscopy shows high-spin iron(II) ions (IS = 1.10 mm.s(-1) and QS = 1.66 mm.s(-1) at 297 K) and high-spin iron(III) ions (IS = 0.42 mm.s(-1) and QS = 1.27 mm.s(-1) at 297 K), suggesting that the anionic layer of iron-chloranilate has a valence-trapped mixed-valence state. At the temperature range of 77-300 K, the compounds 1, 2, and 3 are EPR silent, whereas the EPR spectrum of 4 shows two types of signals with g = 2.008 indicating the radical form of TTF.

Journal Article↗